Summary/Abstract This project will construct a Multigenerational Longitudinal Panel (IPUMS-MLP) of unprecedented scale and scope. Using cutting-edge automatic record linkage technology and drawing on complete count U.S. census data available from IPUMS for the period 1850 to 1940, the project will construct millions of individual life histories and trace millions of families over multiple generations. This infrastructure will provide the most comprehensive view of long-run changes in life-course dynamics available for any place in the world and will transform our understanding of processes of population aging. The work will require significant innovation and new technical infrastructure to accommodate the massive scale of the database. These data will allow investigators to directly observe changes in aging processes and life-course transitions during the period in which U.S. society was being transformed by industrialization, urbanization, immigration, demographic transition, and economic collapse. Investigators will be able to follow individuals over time to evaluate the impact of early-life conditions on later outcomes, trace life-course transitions into adulthood and old age, and observe family change over multiple generations. IPUMS-MLP will enrich existing aging surveys by providing data on multiple generations of forebears of survey respondents; likewise, it will enrich existing historical databases by enabling them to connect with descendants across multiple generations. Leveraging billions of dollars of federal investments in census data and transactional records from a variety of administrative sources, this project is a highly cost-effective use of scarce resources to develop shared infrastructure for research, education, and policy-making on health and aging.